In recent years, as a shift device for an automatic transmission mounted on a vehicle, one of a so-called shift-by-wire system has attracted attention, which is advantageous in downsizing of the device, a reduction in operation force and electronic control. The shift-by-wire system is a switching system by a so-called electric control, in which a sensor or the like detects a shift position in a shift operation unit and then a speed change control device transmits a switching signal to an actuator of the automatic transmission based on the detected signal to thereby switch the range of the automatic transmission.
Here, examples of the common selection range in an automatic transmission include a neutral range, a drive range, a reverse range and a low range. Shift positions in the shift operation unit of the shift-by-wire system also include a neutral position, a drive position, a reverse position and a low position in accordance with each range, respectively.
Moreover, the selection range in the automatic transmission includes a parking range which locks the automatic transmission. This parking range is selected with a parking position provided in the shift operation unit being chosen by a driver by means of a shift lever, or with a parking switch provided separately being depressed by a driver.
Patent document 1 describes an example of the shift device of such a shift-by-wire system and in particular, discloses a technique of preventing abrupt deceleration of a vehicle from being caused when a parking switch is depressed or the like while the vehicle is moving at a predetermined speed.